Methods and apparatus for correcting spectral color measurements

Apparatus for correcting spectral measurements of a color sensing device, said color sensing device obtaining a set of spectral measurements, each measurement representing an amplitude of detected light in a spectral band from a plurality of respective N spectral bands, such that the set of spectral measurements is represented by a 1×N spectral measurement vector, said apparatus comprising:

• an N×N transform matrix that provides mapping between the spectral measurements and corrected spectra;
• and
• a processor for multiplying the 1×N spectral measurement vector by the N×N transform matrix to generate a corrected spectrum;
• wherein said N×N transform matrix is obtained by:
• calculating a set of basis function weighting vectors based on the difference between measured values for a plurality of color samples and a set of reference spectra values for said color samples;
• and
• forming said N×N transform matrix based on said basis function weighting vectors.

A method for correcting spectral measurements of a color sensing device, comprising:

• obtaining a set of spectral measurements, each of said measurements representing an amplitude of detected light in a spectral band from a plurality of respective N spectral bands, such that the set of spectral measurements is represented by a 1×N spectral measurement vector;
• measuring spectra values of K color samples, each sample having a known reference reflectance spectra;
• solving for a set of basis function weighting vectors based on the difference between measured spectra values and the reference reflectance spectra values using a set of D basis functions, where D is less than or equal to the lesser of K or N;
• designating the basis function weighting vectors as an array of D×N amplitudes;
• and
• forming an N×N transform matrix by adding an identity matrix I to the product of the N×D basis set and the D×N amplitude array;
• and
• multiplying the 1×N spectral measurement vector by the N×N transform matrix to generate a corrected spectrum.

Apparatus for correcting spectral measurements of a color sensing device, said color sensing device obtaining a set of spectral measurements, each measurement representing an amplitude of detected light in a spectral band from a plurality of respective N spectral bands, such that the set of spectral measurements is represented by a 1×N spectral measurement vector, said apparatus comprising:

• an N×N transform matrix that provides mapping between the spectral measurements and corrected spectra;
• and
• a processor for multiplying the 1×N spectral measurement vector by the N×N transform matrix to generate a corrected spectrum;
• wherein the N×N transform matrix is obtained by:
• measuring spectra values of K color samples at the color sensing device, each sample having a known reference reflectance spectra value;
• solving for a set of basis function weighting vectors based on the difference between measured spectra values and the reference reflectance spectra values at the processor using a set of D basis functions, where D is less than or equal to the lesser of K or N;
• designating at the processor the basis function weighting vectors as an array of D×N amplitudes;
• and
• forming at the processor the N×N matrix by adding an identity matrix I to the product of the N×D basis set and the D×N amplitude array.